Over the last decade, evidence has mounted that the solar system's observed state can be favourably reproduced in the context of an instability-driven dynamical evolution model, such as the "Nice" model. To date, all successful realisations of instability models have concentrated on evolving the four giant planets onto their current orbits from a more compact configuration. Simultaneously, the possibility of forming and ejecting additional planets has been discussed, but never successfully implemented. Here we show that a large array of 5-planet (2 gas giants + 3 ice giants) multi-resonant initial states can lead to an adequate formation of the outer solar system, featuring an ejection of an ice giant during a phase of instability. Particularly, our simulations demonstrate that the eigenmodes which characterise the outer solar system's secular dynamics can be closely matched with a 5-planet model. Furthermore, provided that the ejection timescale of the extra planet is short, orbital excitation of a primordial cold classical Kuiper belt can also be avoided in this scenario. Thus the solar system is one of many possible outcomes of dynamical relaxation and can originate from a wide variety of initial states. This deems the construction of a unique model of solar system's early dynamical evolution impossible.

Giant planet ejected from the solar system†The solar system may have given up a giant planet and spared the Earth, according to an article recently published in The Astrophysical Journal Letters.Clues suggest that the orbits of giant planets were affected by a dynamical instability when the solar system was only about 600 million years old. As a result, the giant planets and smaller bodies scattered away from each other.Some small bodies moved into the Kuiper Belt and others travelled inward, producing impacts on the terrestrial planets and the Moon. The giant planets moved as well. Jupiter, for example, scattered most small bodies outward and moved inward.Read more

This article relates two topics of central importance in modern astronomy - the discovery some fifteen years ago of the first planets around other stars (exoplanets), and the centuries-old problem of understanding the origin of our own solar system, with its planets, planetary satellites, asteroids, and comets. The surprising diversity of exoplanets, of which more than 500 have already been discovered, has required new models to explain their formation and evolution. In turn, these models explain, rather naturally, a number of important features of our own solar system, amongst them the masses and orbits of the terrestrial and gas giant planets, the presence and distribution of asteroids and comets, the origin and impact cratering of the Moon, and the existence of water on Earth.

The Sun was an order of magnitude more luminous during the first few hundred thousand years of its existence, due in part to the gravitational energy released by material accreting from the Solar nebula. If Jupiter was already near its present mass, the planet's tides opened an optically-thin gap in the nebula. We show using Monte Carlo radiative transfer calculations that sunlight absorbed by the nebula and re-radiated into the gap raised temperatures well above the sublimation threshold for water ice, with potentially drastic consequences for the icy bodies in Jupiter's feeding zone. Bodies up to a meter in size were vaporized within a single orbit if the planet was near its present location during this early epoch. Dust particles lost their ice mantles, and planetesimals were partially to fully devolatilized, depending on their size. Scenarios in which Jupiter formed promptly, such as those involving a gravitational instability of the massive early nebula, must cope with the high temperatures. Enriching Jupiter in the noble gases through delivery trapped in clathrate hydrates will be more difficult, but might be achieved by either forming the planet much further from the star, or capturing planetesimals at later epochs. The hot gap resulting from an early origin for Jupiter also would affect the surface compositions of any primordial Trojan asteroids.

†Jupiter, Saturn, Uranus and Neptune. Those are the gas giants, the four heavyweights of the solar system. But was there once a fifth?Maybe so, says a new study by David Nesvorny of the Southwest Research Institute in Boulder, Colorado. He used computer simulations to explore what the solar system may have looked like some four billion years ago.Read more†

Recent studies of solar system formation suggest that the solar system's giant planets formed and migrated in the protoplanetary disk to reach resonant orbits with all planets inside 15 AU from the Sun. After the gas disk's dispersal, Uranus and Neptune were likely scattered by gas giants, and approached their current orbits while dispersing the transplanetary disk of planetesimals, whose remains survived to this time in the region known as the Kuiper belt. Here we performed N-body integrations of the scattering phase between giant planets in an attempt to determine which initial states are plausible. We found that the dynamical simulations starting with a resonant system of four giant planets have a low success rate in matching the present orbits of giant planets, and various other constraints (e.g., survival of the terrestrial planets). The dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, and leads to final systems with fewer than four planets. Several initial states stand out in that they show a relatively large likelihood of success in matching the constraints. Some of the statistically best results were obtained when assuming that the solar system initially had five giant planets and one ice giant, with the mass comparable to that of Uranus and Neptune, was ejected to interstellar space by Jupiter. This possibility appears to be conceivable in view of the recent discovery of a large number free-floating planets in interstellar space, which indicates that planet ejection should be common.

Marsformed in record time, growing to its present size in a mere three million years, much quicker than scientists previously thought.Its rapid formation could explain why the Red Planet is about one tenth the mass of Earth.The study supports a 20-year-old theory that Mars remained small because it avoided collisions with planetary building material.Read more†

From candy floss to rock: study provides new evidence about beginnings of the Solar System

The earliest rocks in our Solar System were more like candy floss than the hard rock that we know today, according to research published in the journal Nature Geoscience.The work, by researchers from Imperial College London and other international institutions, provides the first geological evidence to support previous theories, based on computer models and lab experiments, about how the earliest rocks were formed. The study adds weight to the idea that the first solid material in the Solar System was fragile and extremely porous - much like candy floss - and that it was compacted during periods of extreme turbulence into harder rock, forming the building blocks that paved the way for planets like Earth.Read more†

When the earliest rocks were formed in the solar system, they looked more like candy floss than the hard rock that we know today, according to a new research. Researchers from Imperial College London and other international institutions made the discovery after highly detailed analysis of a meteorite fragment from the asteroid belt between Jupiter and Mars.The 'carbonaceous chondrite meteorite' was originally formed in the early solar system when microscopic dust particles gathered around larger grain particles called chondrules, which were around one mm in size.Read more†

New research has found when the earliest rocks were formed in the Solar System they resembled fairy floss more than the building material of planets.Scientists made the discovery after highly detailed analysis of a meteorite fragment from the asteroid belt between Jupiter and Mars.Read more†